The present invention relates to a riding lawn mower and a transmission designed for the same and more particularly to a compact riding lawn mower.
Conventional lawn mowers comprise a pair of front ground engaging wheels and a pair of rear ground engaging wheels; front and rear axles coupled to the front and rear ground engaging wheels, respectively; a vehicle frame supported by the front and rear axles; a drive source such as engine mounted on the vehicle frame; a transmission for transmitting drive power from the drive source to the ground engaging wheels after changing the speed of drive power to a desirable degree and; a mower blade to which drive power is transmitted from the drive source. Drive power is transmitted via pulleys and belts from the drive source to the transmission and thereafter to the cutter blade.
In the case of transmitting drive power using pulleys and belts, a tension roller is required to tension a belt. As a result, the rotation axes of the pulleys must be located away from each other to a certain extent. This means that in the case of disposing the drive source and the transmission between the front and rear wheels, for example, the length from the drive source to the rear end of the vehicle frame is (the minimum necessary length L1 between the drive source E and the transmission T)+(the length L2 between the transmission T and the rear axle R) as shown in FIG. 18. In the figure, the symbol M denotes a cutter blade.
There have been various proposals to downsize riding lawn mowers. For example, U.S. Pat. No. 5,367,861 to Murakawa et al discloses a compact lawn mower. The lawn mower of Murakawa et al has a drive source E arranged on the front portion of the frame with respect to a rear axle R, and also has a transmission T arranged on the rear portion of the frame as shown in FIG. 19. This arrangement is based on the consideration that when drive power is transmitted using pulleys from a drive source to a transmission, the length L1 cannot be shortened. According to this mower, the distance between the drive source and the rear end of the frame is the length L1. Accordingly, the overall length of the mower can be reduced by the length L2.
Thus, the lawn mower of Murakawa et al successfully had the overall length reduced by the length L2. However, since the length L1 (from the drive source to the transmission) was not reduced, the entire riding lawn mower was not downsized sufficiently.
The present invention is made to solve the above disadvantages and to provide a riding lawn mower that has a reduced overall size.
To attain the above object, the present invention provides a riding lawn mower comprising: two pairs of ground engaging wheels disposed at front and rear portions of a vehicle frame; a cutter blade supported by the vehicle frame; a drive source mounted on the vehicle frame and having an output shaft extending downwardly; a transmission including i) a casing; ii) an input shaft substantially vertically supported by the casing, and iii) a pair of axles extending substantially horizontally in opposite directions, the pair of axles supporting each one of the two pairs of ground engaging wheels, the transmission being arranged below the drive source and having the input shaft that is coupled substantially coaxially with the output shaft of the drive source to rotate together; and a power transmitting member for the cutter blade, the power transmitting member being provided to rotate with the output shaft.
Preferably, the riding lawn mower comprises an adjuster for adjusting the alignment of the axes of the output shaft and the input shaft of the transmission.
Preferably, the drive source on the vehicle frame is disposed between the two ground engaging wheels.
Preferably, the lower end of the output shaft of the drive source is coupled via a bearing with the upper end of the input shaft of the transmission to ensure uniform rotation.
Preferably, a power transmitter for the cutter blade is provided on the outer surface of the coupling.
Preferably, the power transmitter for the cutter blade is used as a pulley and a belt, a space is provided between the lower end of the drive source output shaft and the upper end of the transmission input shaft to receive the belt, and the coupling is axially slidably mounted on the output shaft or the input shaft so that the coupling can take the positions of closing and opening the space, respectively.
Further, in order to attain the above object, the present invention provides a transmission comprising: a casing; an input shaft substantially vertically supported by the casing; first and second intermediate shafts substantially horizontally supported by the casing; a pair of axles substantially horizontally supported by the casing and extending from the casing in opposite directions; a gear train for transmitting the rotation of the input shaft to the first intermediate shaft; a friction clutch supported on the first intermediate shaft; a driving speed-change gear train rotatably supported on the first intermediate shaft; a driven speed change gear train rotatably supported on the second intermediate shaft and meshing with the driving speed-change gear train; a shifter supported axially slidably on the second intermediate shaft non-rotatably relative thereto, wherein the shifter meshes one gear of the driven gear train with the second intermediate shaft in accordance with its axial position; an output gear provided or integrally formed on the second intermediate shaft non-rotatably relative thereto; and a differential gear meshing with the output shaft and transmitting drive power from the output shaft to the pair of axles, the friction clutch including: a driving friction member having a conical friction surface and supported on the first intermediate shaft in a non-rotatable and axially slidable manner; a driven friction member having a friction surface corresponding to the conical friction surface, rotatably supported on the first intermediate shaft and coupled with the driving gear train; and a clutch arm for sliding the driving friction member for engagement with the driven friction member.
Furthermore, the present invention provides a transmission comprising: a casing; an input shaft substantially vertically supported to one side of the casing; first and second intermediate shafts substantially horizontally supported in this order by the casing along a front and rear direction of a vehicle frame; a pair of axles substantially horizontally arranged behind the second intermediate shaft and extending outside of the casing in opposite directions; a gear train for transmitting the rotation of the input shaft to the first intermediate shaft; a driving speed-change gear train rotatably supported on the first intermediate shaft, wherein the driving speed-change gear is located to the input shaft along the first intermediate shaft; a friction clutch supported on the first intermediate shaft, wherein the friction clutch is located opposite the first input shaft along the first intermediate shaft, the friction clutch engaging and disengaging the first intermediate shaft with or from the driving speed-change gear train; a driven speed-change gear train rotatably supported on the second intermediate shaft, the driven speed-change gear train correspondingly meshing with the driving speed-change gear train; a shifter rotatably and axially slidably supported on the second intermediate shaft, wherein the shifter is located to the input shaft along the second intermediate shaft, the shifter means engaging one gear of the driven speed-change gear with the second intermediate shaft in accordance with its axial position; an output gear provided on or integrally formed on the second intermediate shaft non-rotatably relative thereto, wherein the output gear is located opposite the input gear along the second intermediate shaft; and a differential gear arranged opposite the input shaft in the casing, the differential gear meshing with the output gear to transmit drive power to the pair of axles.